Carrier transport and photoluminescence properties of Ga-doped ZnO films grown by ion-plating and by atmospheric-pressure CVD

• Ga-doped ZnO films were prepared by atmospheric-pressure CVD and ion-plating.
• The ∆μ/∆T plots for the CVD-GZO films obey those for the IP-GZO films.
• Carrier concentration dependences of PL and PLE properties were examined.
• PL and PLE spectra of the GZO films changed markedly at n = 4.0 × 1019 cm− 3.

Ga-doped ZnO (GZO) films with carrier concentrations ranging from 5.2 × 1017 to 2.9 × 1020 cm− 3 were grown on r-plane sapphire substrates by atmospheric-pressure CVD (AP-CVD). The gradients of Hall mobility (μ) — temperature (T) curves (denoted by Δμ/ΔT) for the GZO films grown by AP-CVD (CVD-GZO films) plotted as a function of carrier concentration n obey those for the GZO films deposited by ion plating with dc arc discharge (IP-GZO films). This suggests that the dominant carrier scattering mechanism limiting the carrier transport is common between the CVD-GZO and IP-GZO films at any given n. The CVD-GZO films with low n exhibited the Ga-related neutral donor bound exciton and two-electron satellite (TES) lines at low temperature. With increasing n, the above two characteristic lines shifted higher energies accompanied by broadening. The IP-GZO films exhibited two emission lines with opposite n dependences; with increasing n, one line shifted towards higher energies, whereas another line shifted towards lower energies. With an increase in n caused by the donor doping, the relaxation of the momentum-conservation law brought the remarkable changes to the PL and PLE spectra of both the IP-GZO and CVD-GZO films with n of more than 4.0 × 1019 cm− 3 that is close to the Mott density.